Researchers from Stanford University in US created the technology that may someday serve as the basis for quantum communication.

In the physics of quantum communication, standard lasers are actually not useful for secure communication because they emit what is called 'classical' light.

Data eavesdroppers could extract any data being carried via classical light without detection. In contrast, a quantum internet would be based on 'quantum' light, in which a single unit of light - a single photon - cannot be measured without being destroyed.

Researchers have been working for years to develop various nanoscale lasers and quantum technologies that might help conventional computers communicate faster and more efficiently using light instead of electricity.

They realised that a modified nanoscale laser can be used to efficiently generate quantum light for communication.

"The problem is that the quantum light is much weaker than the rest of the light coming from such a modified laser - it is difficult to pick up," said Jelena Vuckovic from Stanford University.

"So, we created a way to filter out the unwanted light, allowing us to read the quantum signal much better," Vuckovic said.

The filtering works in a fashion similar to the way noise-cancelling headphones operate, only with light, instead of sound, researchers said.

With the headphones, a sensor actively gauges the frequency of relatively constant ambient sound - the rumble of traffic, the drone of an airplane engine, the thrum of a refrigerator - and produces a similar pattern, which can be used to cancel out the undesirable sound.

"Some of the light coming back from the modified laser is like noise, preventing us from seeing the quantum light. We cancelled it out to reveal and emphasise the quantum signal hidden beneath," said Kevin Fischer from Stanford University.

Researchers adapted an interference technique borrowed from 1930s-era radio engineering to cancel the unwanted classical light.

They first figured out what the 'noise' looks like and played it back. By carefully adjusting how the cancelling light and the classical light overlap, the unwanted light is cancelled and the once-hidden quantum light is shown.

"It provides us with a practical pathway to secure quantum communications," said Vuckovic.

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